1. Field of the Invention
The present invention relates to optical communications, more particularly to components for optical circuits intended to improve bonding, fixing and mounting of optical waveguide with optical fiber and semiconductor device in a module using optical waveguide, and a method of manufacturing the same.
2. Description of the Prior Art
The advance of optical communications is dramatic recently, and applications and practical use are promoted in public communications, CATV, computer networks, etc. From the viewpoint of components, however, there are problems for reduction of size and enhancement of mass producibility in order to spread more widely. For example, an optical transmitter-receiver comprises a laser driving circuit, a photo detector, a demodulating circuit, and optical fibers. It is required to adjust, assemble, and mount these optical and electrical components at high precision. Many components and assembling processes are needed. Further distribution of optical communication systems demands smaller size, multiple functions, higher degree of integration, and lower cost of components for optical circuits. In particular, for installation of subscriber optical communication systems, reduction of size and lowering of cost of components for optical circuits are important subjects.
On the other hand, required functions of subscriber system include, among others, the functions of wavelength division multiplexing and bi-directional transmission by making use of the broad band properties of optical communications. For integration of functions, several optical circuit submounts using optical waveguide have been proposed. For example, according to a proposed optical module, a silica-based optical waveguide is formed on a silicon submount by flame-hydrolysis deposition, and further metal electrodes are wired, and semiconductor devices and electric circuits are mounted, and optical fibers are arranged and connected on the submount forming V-grooves.
In such conventional components for optical circuits, the submount mounting optical waveguides, light emitting devices, light receiving devices, and electrode wiring is separate from the submount for fixing optical fibers. To bond the optical waveguide and optical fibers at low loss, it is required to adjust, assemble and fix at a precision of 1 micro-m or less. For fabrication of submount for fixing optical fibers, selective etching of silicon submount, and V-groove method by cutting ceramic submount are employed. They have their own problems in processing precision and mass producibility. In the silicon submount, a precise V-groove can be formed by etching, but since the shape is limited to V-form, the restrictions on processing shape are large. It is also required to match the crystal orientation of etching mask and silicon submount at high precision. Furthermore, if the materials of optical waveguide submount and groove submount are different, they differ in the coefficient of linear expansion, and therefore the characteristic varies with temperature fluctuations. When mounting semiconductor devices and electric parts on a silicon submount, it is necessary to form an insulation layer on the submount. If semiconductor devices are directly formed on the silicon submount, the area occupied by the optical waveguide increases, and the number of devices obtained from one wafer is small, and the cost is not lowered.